Methods, by which pyridine bases are produced by reacting an aliphatic aldehyde and/or ketone with ammonia in gaseous phase using a solid acid catalyst such as amorphous aluminosilicate and the like, are known (Japanese patent application Kokai (Laid-Open) No. 63,176/76, Japanese Patent Publication Nos. 41,546/71, and 32,790/69).
It is known that crystalline aluminosilicate, so-called zeolite is used as the catalyst for producing pyridine bases from an aliphatic aldehyde and/or ketone and ammonia (U.S. Pat. No. 4,220,783 and Japnese patent application Kokai (Laid-Open) No. 38,362/85).
In the methods using amorphous aluminosilicate catalyst which are practiced industrially the yields, which are calculated based on the total number of carbon atoms of an aliphatic aldehyde and/or ketone, are as low as 50% at most and carbon is deposited on the catalyst due to side reactions, resulting in lowering of the activity within a short time. Therefore, it is necessary to reactivate the catalyst by periodical regeneration by aeration, and the repetition of reaction (deposition of carbon) and regeneration (overheat) brings deteriorations of catalytic activity and of mechanical strength of the catalyst.
Even when a zeolite is used as the catalyst, for example, U.S. Pat. No. 4,220,783 discloses that pyridine was obtained in such low yield as 40% by using an H form ZSM-5 or a ZSM-5 ion exchanged with cadmium, copper or nickel. Japanese patent application Kokai (Laid-Open) No. 38,362/85 discloses that acetaldehyde, formaldehyde and ammonia were used and in the case of fixed bed, the total "yield" of pyridine and .beta.-picoline was 77%, the "yield" of pyridine which is more expensive than .beta.-picoline economically being 51%. In the case of fluidized bed which is superior reaction system, the reaction was effected by using the same catalyst to obtain pyridine and picolines in a total "yield" of 88.8%, the yield of pyridine being 60.2%.
However, the yields are shown as the values calculated based on the amount of the acetaldehyde alone out of the amounts of acetaldehyde and formaldehyde (molar ratio of 1:1) used in the reaction, and if the yields are converted into the values calculated based on the total carbon number of acetaldehyde and formaldehyde, the total yield of pyridine and picolines is changed from 88.8% to 78.5% and the yield of pyridine is changed from 60.2% to 51.7%.